Overhead garage door



July 23, 1 J. H. M KEE OVERHEAD GARAGE DOOR Filed 001;. 9, 1926 3 Sheets-Sheet July 23, 1929. I

J. H. M m-:5

OVERHEAD GARAGE DOOR Filed 001;. 9, 1926 3 Sheets-Sheet .mwmi

July 23, 1929. MCKEE 1,721,501

OVERHEAD GARAGE DOOR Filed Oct. 9, 1926 5 Sheets-Sheet 3 Patented July 23, 1929.

UNITED STATES JAMES H. MCKEE, OF HARVEY, ILLINOIS.

OVERHEAD GARAGE DOOR.

Application filed October 9, 1926. Serial No. 140,443.

This invention relates to overhead doors of the type used in connection with garages, factories, warehouses, or other buildings, such as piers or docks, and the like, and which, when open, are disposed in an overhead positionthat is, slightly inclined or horizontal over or above the door opening and extending therefrom and adapted to roll or slide downwardly to a vertical position when closed to cover the doorway, thereby cconomizing in space at the door opening or in an alleyway when the door is open and avoiding obstruction in a doorway, roadway, or alley, as well as enhancing the appearance of the building or garage. This is also important in connection with the doors on piers or docks; in fact, any building where economy of space and sightliness are important, as they most always are.

The objects of the invention are to provide an improvement upon the structure shown in my prior application, Serial No. 118,878, filed June 28, 1926, and especially to provide a more compact and simple structure for accommodating the door--that is, the counterbalancing or counterweighting means thereof, so that they can be sold in smaller units, capable of more economical production, and at the same time produce a counterweighting effect in which the effective weight of the door, is varied, as well as the leverage of the balancing force, this variance being preferably proportional or. harmonious, so that the two will equalize or more nearly equalize each other than in prior structures when the door is operated, whereby the opening and closing of the door may be accomplished with little or no manual effort, so that a child can conveniently open the door or close it.

The counterbalancing or counterweighting means is so constructed that it preferably operates to uniformly graduate or vary according to the position of the door so as to relieve the operator of excessive strain in opening and closing the door but providing the greatest leverage or counterbalancing effectto counteract the weight of the door when it is closed and the least when the door is open. Thisleverage uniformly and harmoniously increases as the door moves from an open to a closed position and decreases as the door moves from a closed position to an open position, whereby the Weight of the door will at all times be accurately counterbalanced and sustained, thus preventing it from being difficult to open or closing with a slam, and obviating other objectionable features heretofore found in doors of this type.

Other objects of the invention are to provide novel, compact units for mounting the drum or sheave on which the cable is Wound or spooled and the association of a spring, preferably a spiral spring therewith, constituting counterbalancing means, said means being so mounted as to act individually upon the opposite sides of the door, whereby the door is prevented from operating unevenly and binding at one side due to its tendency to operate in a canted position.

The invention embodies all of the important and desirable features of my prior device, such as guiding means for the door and means to prevent it from rattlin means to permit automatic closing of the c oor in case of tire, and a novel construction for the coun terweighting or counterbalancing means, so that when the door is closed or nearly closed the greatest counterbalancing effect will be produced, and when open or nearly open the least counterbalancin effect will be produced, this counterba ancing force gradually decreasing uniformly as the door is open and increasing uniformly as the door is closed, for the purposes heretofore pointed out.

apparent as the description proceeds.

In the accompanying drawings Fig. 1 is a sectional elevation showing a portion of a garage or other building provided with an overhead door and the counterbalancing means of my invention, the door being shown closed in solid lines and open in dotted lines.

Fig. 2 is a horizontal sectional View taken on the line 22 of Figure 1.

Fig. 3 is a sectional elevation similar to Figure 'l but showing a modified arrangement.

Fig. 4 is a vertical sectional view of one of the fittings or counterbalancing means.

Figs. 5 and 6 are sectional views taken on the lines 5-5 and (i6 of Figures 6 and 5 respectively.

Fig. 7 is a sectional view corresponding to Figure 6, of a modification in which a frusto-conical drum is employed in lieu of a sheave, and

Figs. 8, 9, and 10 are plan views of further modifications.

Referring to the drawings in detail, :1 ga- Further objects and advantages will be rage or other building is shown having a front wall 5 equipped with door frame or jambs 6 providing a doorway 7 which has a door stop 8. The side walls of the garage or building are designated at 9 and may be connected by suitable joints, girders, or rafters and ties. 10 is a bracket or supporting piece, and 11 is either side studding, brackets, or supports hung from the joist, purlins, or ties, while the rear wall or a suitable vertical support arranged at a proper distance from the front wall 5 and at about the same elevation as the top of the doorway 7, is designated at 12. These constructional features of the garage or building form no part of the novelty of the invention and may be varied according to the particular requirements.

Arranged against the door frame 6 or stops 8 at the inside are sectional tapered closing strips 13, fastened to the door, these strips being thickest at the top and tapering downwardly to the bottom of the front of the garage or door, as clearly seen in the drawings. Disposed inwardly in spaced relation to the door frame and the strips 13 are brackets 14 and guide rails or tracks 15 which extend vertically at the sides 9 and may be of right-angular, channel, grooved, or of other construction. The guide rails or tracks 15 have curved portions 16 at the top extending upwardly and rearwardly into substantially horizontal upper portions 17, which, however, are preferably slightly inclined toward the doorway to give slight impetus to the closing of the door and for fire purposes in the automatic closing thereof, as will be more fully described hereinafter.

The door is preferably of the paneled or slatted type, being composed of a plurality of sections, preferably three in number and indicated at 18, 19, and 20. These sections have co-acting rabbeted edges 21 interfitting to provide a weather-tight joint while allowing the necessary angular movements of the sections'relatively in moving from a vertical to a horizontal position or vice versa, owing to the angular movements required in passing over the curved portions 16 of the guide rails or tracks. Anti-friction rollers 22 are provided at the sides and lower edges of the lower section 18, these rollers having their shafts 23 journaled in brackets 24 secured to the inner face of this section of the door and the rollers engaging the retainers or track 15. Similar rollers 25 are mounted on the pivots 26 of hinges 27 connecting the sections 18 and 19 and the sections 19 and 20, the pivots being in line with the edges of thesections so that the wheels will travel in contact with the retaining flanges of the guide rails at the side of the garagenor building without shifting of the centers thereof, such as will happen if the pivots wereoutof alignment with the edges or center of the arcs in which the section swung relatively when the door is moved over the curved portions 16 from a closed to an open position or an open-to a closed position. At the same time these rollers permit the door to be moved without undue friction and cause it to press the tapered closing strips 13 against the jamb 6 and stops 8 at the sides and top of the doorway, whereby the doors are maintained tight when closed, thus giving a desirable weather-tight joint and avoiding gapping or rattling which is so prevalent in ordinary garage or similar doors. A similar roller or track wheel 28 is provided near the upper edge of the upper section 20, but preferably, in a position adjacent the inwardly curved portions 16 of the tracks or guide rails when the door is closed, as shown especially in Figure 1.

The qounterbalancing mechanism includes flexible members or cables 29 which extend down along the sides or side edges of the door and are anchored near the bottom thereof in any suitable manner as indicated at 30. These cables extend upwardly and are trained over sheaves or pulleys 31 journaled in suitable brackets 32 carried by the support 10 at cal support or rear Wall 12 of the garage or other building, or at any other suitable position, and have their ends anchored in the sheaves 33. Specifically, these sheaves are journaled on shafts 35, one end or half the length of which is round to take the sheave and extends through an opening in one side of the bracket 34 where it is held by a gib key or the like 36. The other end or half is squared as indicated at 37 and engages a corresponding square or polygonal shaped opening in the opposite side of the bracket and is held by a similar key 38, although it is to be understood that any other securing means may be employed to hold the parts assembled. In the preferred form, the sheave wheel or drum 33 extends beyond the bracket and the groove thereof is sufliciently deep to accommodate the length of cable 29 which is adapted to wind thereon so that the turns are disposed on top of one another to the periphery of the sheave when spooled. The squared portion 37 has one end of a spiral spring 39, as distinguished from a helical spring, anchored thereto, as indicated at 40. This spring has the other end anchored to one side of the sheave 33 as indicated at 11, so as to wind the spring when the cable is unwound from the sheave and the door is closed, thereby exerting its greatest tension to raise the door or counterbalance its weight. It is to be especially noted from Figures 1, 5, and 6 of the drawings, that the inner turn of the cable at the bottom of the groove is disposed inwardly of the outer turn or convolution of the spring or near the axis, while the outer turn or convolution of the cable when wound on the sheave is positioned'outwardly of the outer convolution of the spring, so that the greatest leverage or counterbalancing effect for opening the door is exerted when the door is closed and the least leverage and tension of the spring are exerted when the door is open, the leverage, due to the different tensions of thelsprings when wound and unwound and the relation thereof to the lever arm or radius of the cable, due to its distance from the axis in the different positionsthat is, when" wound or unwound, being opposite. In this manner the leverage of the counterbalancing or counterweighting means produced by the spring, each acting individually at opposite sides of the door, will uniformly decrease as the door is raised to open the same and uniformly increase as the door is lowered to close the same, so that the weight of the door will at all times be approximately sustained or balanced, whereby the door can be opened with little manual effortand closed without slamming.

It will thus be seen that by having one of these counterweighting or counterbalancing elements acting on each side of the door and operating individual drums or sheaves with independent cables, there will be no tendency to act unevenly at opposite sides or edges of the door, such as would cause the door to cant and bind in the frame or guideways thereof at opposite sides of the door. On the other hand, each spring works on its cable and they can be set to operate alike so that each drum is moved the same, thus overcoming the objection to devices employing a'single torsion spring usually of the helical type, wherein should a cable or belt attached to and hanging from the drums on one side stretch more than the one on the other side or should one be set more loosely or slip a little, then the one stretching the most would be loose and throw practically all of the weight on the other cable and spring tending to lift the door on one side and cause cramping or binding. By having the double'spring arrangement, one on each side of the door, the springs themselves will take up and compensate for stretching or slacking in the cables and cause'the latter to operate evenly. In the form shown in Figures 1 and 2, the counterbalancing elements are mounted in the back while in the form shown in Figure 3 the construction is the same except that the brackets and'counterbalancing elements are mounted at the front or over the doorway of the garage with the cables extending straight down to the side edges of the door at the bottom. In either device, when the door is closed, the cables are unwound from their individual sheaves 33, which results in the winding of the springs 39 to put them under greater tension. The points at which the cables extend from the sheaves have, therefore, been transferred or shifted from points radially outwardly of the outer turn of the springs to the bottom points of the grooves of the sheaves or radially inwardly of the outer turns of the springs. By this action the effective weight of the door itself, is varied and also the weight of the counterbalancing force orcounterweighting means comprised by the springs, in order that the two will exactly equalize each other in operation. In other words, in the position referred to the effective weight of the door will be decreased due to the lever arm thereof being shortened by reason of the radial extension of the cable from the sheave or drum being shifted from a point without the spring to a point inwardly of the same, while the leverage of the spring will be increased and the tension will be greater due to the winding thereof. This variation will be gradual and uniform and will automatically vary and compensate for the load according to the position of the door,,inasmuch as it gradually and uniformly decreases as the door is opened and similarly increases as the door is closed. When the door is closed or moves downwardly the force of the spring is increased but when the door is raised and the cable is wound on the sheave while the spring is unwinding and loosening its tension, or some of it, so that the spring is exerting less force as the effective weight of the door decreases. This variation in the affective weight of the door and the counterbalancing and counterweighting effect of the-springs are gradual and uniform, this regularly graduatingvariation being compensated for when gradually and uniformly increasing as the door moves to its elevated position and the outer lap or convolution of the cable or belt is wound on itself or moved to a larger portion of the drum. This leverage similarly decreases as the door is closed due to this lap of the cable moving to the small portion of the drum, the variation in the leverages compensating for the load sustained according to the position of the door, with the result that the door moves uniformly and evenly and may be easily opened and closed .Without slamming and with a minimum of manual efiort.

In the constructions shown in Figures 1 to 6 inclusive a sheave or pulley type of drum is employed, but it is to be understood that any suitable compensating variable ratio single drum may be employed as distinguished from double drums and that they may be made spiral or plain, and concave or convex. In either instance, a plurality of fusible links 42 may be positioned in the length of each cable 29 which, in conjunction with the inclined upper portions of the tracks, will serve to permit the door to automatically close, especially where a steel or other fire-proof door is used. This would result from the breaking of the suspension cables when one of the links melts to permit the door to automatically move down under its own weight and close the doorway, thereby rendering the device especially convenient in connection with garages and other fire-proof buildings, warehouses, pier sheds, and the like.

In-the arrangement heretofore described, it will be noted that the device combines two variable leverages, namely, that of the door and that of the counterbalancing or counterweighing means formed by the springs, so that when the door is closed the effective weight thereof is greatest. As the door is raised and the leverage becomes less, the cables are wound on themselves and operate in larger circles to produce a greater leverage while the leverage of the springs is less.

In the structure showiyin Figure 7 of the drawings, a bracket 43 is provided and is bolted to a suitable vertical support 12, as previously described in connection with the bracket 34, as indicatedat 44, this support being the back of the garage or other upright at a suitable distance from the door and may be suspended from above. The spring is designated at 45 and the shaft at 46 having a rounded portion on which a frusto-conical grooved drum 47 is journaled. This drum is connected to one end, of the spring as at 48, the other end of the spring being anchored to the squared portion 49 of the shaft, so that the spring will act to normally wind the cable on the drum. The shaft is held from displacement endwise and is also held from rotation by the squared portion fitting in a square opening in the bracket as described in connection with the form of the device shown in Figures 4, 5, and 6. It is also to be understood that any'suitable locking means may be provided for the door.-

In the form shown in Figure 8 a bracket 5-0 is provided extending across the width of the door and having end portions 51 in which a shaft 52 is journaled. This shaft is acted on by a spring 53 mounted in a bracket 54 similar to the bracket 34 to which one end of the spring is connected as indicated at 55 while the other end is connected to the shaft 52 to operate it. Suitable sheaves ordrums 56 are secured to the ends of the shaft as indicated at 57 so that the-spring exerts tension for winding the cable on both drums, and the corresponding relation of the leverage is also produced. If one cable should be longer than the other this will be adjusted at the sheave so that even pull will be exerted on opposite sides of the door.

The construction shown in Figure 9 isthe same as that shown in Figure 8 except that in lieu of the frusto-conical drums 56 shown in Figure 8, the shaft 52 carries pulleys or sheaves 58 fixed to the shaft, as indicated at 59, and operates in the same manner as de- In the form shown in Figure 10 each drum or sheave is mounted on an individual shaft or bracket 60 carried by the support 12 or the bracket 50. Each drum or sheave is acted on by a separate spring 61, in this instance shown to be of the helical type having one end anchored to the bracket 60, as indicated at 62, and the opposite end anchored to the drum or its hub as indicated at 63. A spring is mounted on each shaft, and while I have shown helical springs, it is to be understood that adjustment of the cables to operate the door evenly maybe easily accomplished.

It will be especially noted that with the use of a spiral spring or a plurality of coil springs, preferably a pair with one at each side of the door, a very compact and easily mounted structure is provided, as distinguished from one employing a coil or helical torsion spring on asingle shaft with drums at each end. However, I may employ two spiral torsion springs on individual shafts and acting on corresponding drums or sheaves, as shown in the drawings, and obviate the objection to a structure employing a single shaft with drums on each end. In

my device the springs operate directly on the drums in the preferred construction and not directly on the shaft. By employing an overhead track, when the door is up on the track in a raised or open position, it exerts little weight against the drums and springs but has a greater leverage than the springs by reason of the cables being wound on the spools or drums andthe outer windings of the cables are outwardly of the points of connection of the springs to the sheaves or spools and thus have a greater radius, producing a greater leverage than the springs, at which time the springs are under less tension by reason of being unwound.

In the form of the invention shown in Figure 3, instead of having the door-stop 8 set at an angle or forward inclination and with the tracks 15 at the sides of the doorway 7 disposed vertically together with the tapered strips 13 for tightening the door when closed,

the door-stop 8 is set vertically while the track 15 is set at an angle or inclination inwardly or rearwardly and the door 19 follows this track so that the closing strips 13 will tighten the door when closed in the same manner as heretofore described. Furthermore, instead of having the drum mounted on a support 12 at or near the rear ofthe garage, either the drum 42 or single sheave 33 maybe mounted on a bracket 34 at the front of the garage and the spring 39 is anch dredlowthe shafaiaas indicatm scribed in connection with Figure J :fifd connected to the cable 29 which extends around the drums or sheaves and is anchored to the sides of the door near the bottom in the same manner as heretofore described.

In either instance the door will be guided in its movements by the tracks or guide rails and by means of the strip at the top of the door and the beveled strips at the side thereof made in lengths or sections to correspond with the sections of the door, the door will be tightly closed against the door frame or stops without any rubbing or dragging and when the door reaches its. closed position it will be held tight by the beveled strips at the side pressing against the door-jamb, frame, or stops, thus producing a tight fit and one that will easily free itself when the door is open.

In case the heft or weight of the door is greater or twice as great, a s ring may be attached to each end of the sha t 35, in which case space is allowed between both sides of the drum or pulley and the sides of the bracket 34. It is also to be understood that instead of squaring the shaft it can be splined or grooved for the attachment of the end of the spring as is common in the art. Of course, the second spring may be mounted on any of the shafts in any suitable way and this will obviate the necessity of having a larger spring, although, where permissible, the increased weight may be compensated for by a larger spring.

While the relative positions of the coil spring and cable when the door is in open position and when the door is in closed posi tion as disclosed, is desirable from a practical point of view, it is not desired to limit to this form as it is apparent that the principle of the invention is-not at all dependent upon these relative positions. Wherever the term lever arm or leverage is used, the product of the force exerted on the distance from the axis of the sheave of the cable is meant. As a consequence, it will be seen that the case defines three variables, namely, the variable load or effective weight of the door as it is moved to its open position where its weight is supported by a track and vice versa; the variable pull or tension of the spiral spring and the variable lever arm or leverage which is the distance of the cable from the center of the sheave. As the cablev is wound up, the lever arm increases, and at the same time the door is moved to its closed position with a consequent increase in its effective weight. As the cable is payed out, the lever arm decreases, the spring uncoils and the door is moved to its closed position with its load or effective weight sustained by the tracks. The design is such, with respect to these various elements, that a fine counterbalance is maintained.

While I have shown and described my in vention in a preferred form, I am aware that various changes and'modifications may be made without departing from the rinciples of the invention, the scope of whic may be determined by reference to the appended claims.

I claim as my invention:

1. In an overheaddoor, a track adapted to guide a door from a vertically closed position to a substantially horizontal open position above the doorway, a shaft, a drum rotatable on the shaft, and a coil spring connected to the shaft and to the drum and encircling the shaft, said drum having operative connection with the door."

2. In a door of the class described, a doorway, tracks adjacent the doorway and extending to inclined positions above and away from the same, a door movable in said tracks to a substantially vertical position when closed and over the doorway when open, cables connected to the door, brackets suitably supported at points slightly above the top of the door, shafts mounted in the brackets against turning, sheaves rotatable on the shafts and having the cables connected thereto, and springs connected to the shafts and sheaves to exert ,theirtension-and wind the cables on the sheaves to raise the door and winding to resist the downward movement of the door and unwinding of the cables from the sheaves, whereby slamming of the door is prevented.

3. In a door of the class described, a doorway, tracks adjacent the doorway and extending to inclined positions above and away from the same, a door movable in said tracks to a substantially vertical position when closed and over the doorway when open, cables connected to the door, brackets suitably supported at points slightly above the top of the door, shafts mounted in the brackets against turning, sheaves rotatable on the shafts and having the cables connected thereto, and coil springs, the outer ends of the springs being connected to the sheaves at one side of each.

4. A closure for garage doorways and the like, comprising a. door supported to exert its greatest efi'ective load when in a closed position and its least effective load when in an open position, a rotatably mounted drum, a cable operating on the drum and adapted to wind thereon, and a coil spring having one of its ends connected to the drum to rotate the same and the other end connected to a stationary or fixed element adapted to resist with gradually increasing force due to the windin of the spring the unwinding movement of the drum to permit closing of the door.

5. A closure for garage doorways, comprising a variable efi'ective weight door supported to exert its greatest efi'ective load when down and its least effective load when up and supported in an inclined overhead position, a bracket, a shaft fixed onthe bracket against rotation, a drum adapted to rotate on the shaft, a cable operating on, the drum and adapted to wind thereon, and a coil spring mounted around the shaft at one end and connected to the drum to rotate the same and at the other end to a fixed element to resist with gradually increasing force the unwinding movement of the drum to release the cable and permit closing of the door in balanced relation to the variable effective weight of the door.

6. In a door of the class described, a doorway, tracks adjacent the doorway and extending to inclined positions above and away from the same, a door movable in said tracks to a substantially vertical position when closed and over the doorway when open, cables connected to the door, brackets suitably supported at points slightly above the top of the door, shafts mounted in the brackets against turning, sheaves rotatable on the shafts and having the cables connected thereto and coil springs, the outer ends of the springs belng connected to the sheaves at one side of each of said sheaves.

7. In a device of the character described, a movable door, means engaging the door and formed to gradually and increaslngly sustain the weight of the door from its closed to its open position, a sheave, means connecting the sheave with the door, and counterbalancing means connected with the sheave and with a base for gradually and decreasingly urging said sheave to'rotate as the door is opened thereby to counterbalance the weight of the door inits'movement from the closed to the open position, and said sheave being formed to vary the leverage exerted upon the door to decrease said leverage as the door is moved to its closed position.

8. In a device of the character described,

a movable door, means engaging the door and formed to gradually and increasingly sustain the weight of the door from its closed to its open position, a sheave, a cable connect 5 ing the sheave with the door, and a spring device engaging the sheave at one end and a fixed base at the other, said spring adapted to actuate said sheave to wind said cable thereon to sustain the weight of said door in its movement from a closed to an open position, and to resist movement of said sheave as the door is moved to its closed position, and said sheave being formed to vary the leverage or lever arm exerted upon the door by the cable to decrease said leverage as the door is moved to its closed position thereby to more efiectively counterbalance the door.

9. In a device of the character described, a movable door, means engaging the door and formed to gradually and increasingly sustain the weight of the door from its closed to its open position, a rotatable sheave, a cable wound on the sheave and connecting the sheave with the door, a coil spring engaging said sheave at one end and a fixed base at the other to unwind as the door is moved to its open position and to wind up as the door is moved to its closed position, and said sheave being formed to vary the leverage of the cable and the consequent force exerted upon the door and to decrease said leverage as the door is moved to its closed position and increase said leverage as the door is moved to its open position thereby to more effectively counterbalance the door.

10. In a device of the character described, a movable door, means engaging the door and formed to gradually and increasingly sustain the weight of the-door from its closed to its open position, a rotatable sheave, means wound on the sheave and connecting the sheave with the door, a coil spring engaging the sheave at one end and a fixed base at the other to unwind as the door is moved to its open position and to wind up as the door is moved-to its closed position, and said sheave being formed to vary the lever arm through which said connecting means operates on the door to decrease said leverage as thedoor is moved to its closed position and increase said leverage as the door is moved to its open position thereby to-more efiectively counterbalance the door.

11. In a device of the character described, a movable door, means engaging the door and formed to radually and increasingly sustain the weight of the door from its closed to its open position, a shaft having a squared portion and fixedly mounted on a base, a sheave rotatably mounted on the shaft, means wound on the sheave and connecting the sheave with the door, a spiral spring mounted with one of its ends connected to the squared portion of the shaft and the other end'connected with the sheave to unwind as the door is moved to its open position and to wind up as the door is moved to its closed position, and said sheave being formed to vary the lever arm through which said connecting means operates on the door to decrease said lever arm as the door is moved to its closed position and to increase said lever arm as the the door is moved to its open position theregy -to more effectively cofunterbalance the oor.

12. In a device of the character described,

a movable door, means engaging the door and formed to gradually and increasingly sustain the weight of the door from its closed to its open position, a bracket, a sheave rotatably mounted in the bracket, means wound on the sheave and connecting the sheave with door, a spiral spring having one end fixed in the bracket and the other end secured to the sheave to unwind as the door is moved to its open position and to wind up as the door is moved .to its closed position, and said sheave being formed to vary the lever arm through which said connecting means operates on the door to decrease said lever arm as the door is moved to its closed position and to increase said lever arm'as the door is moved to its open position thereby to more efiectively counterbalance the 'door.

13. In a device of the character described, a sectional, movable .door, a track for the door and formed to gradually and increasingly sustain the weight of the door frogn its closed position to its open position, a bracket, a sheave rotatably mounted in the bracket, a cable wound on the sheave and connecting the sheave with the door, a spiral spring having one end fixed in the bracket and the other end secured to the side of the sheave to unwind as the door is moved to its open position and to wind up as the door is moved to its closed position, and said sheave being formed to wind the cable thereon coil over coil thereby to vary the lever arm through which the cable operates on the door, to decrease said lever arm as the door is moved to its closed position and to increase said lever arm-"as the door is moved to its open position thereby to more effectively counterbalance the door.

14- In an overhead door, a track adapted to guide a door from a substantially vertical closed position to an inclined substantially horizontal open position above the doorway, a bracket, a drum rotatable in the bracket, and a coil spring connected to the bracket and to the drum and actuating the latter, said drum having operative connection with the door.

15. In a door of the character described, a movable door, means engaging the door and formed to gradually and increasingly sustain the weight of the door from its closed to its open position, individual fixed brackets, individual rotatable drums mounted in said brackets, flexible connections between the drums and the door and adapted to wind on and unwind from the drums, individual torsion springs engaging the drums at one end and the fixed brackets at the other to unwind as the door is moved to its open position and to wind as the door is moved to its closed position, thereby effectively counterbalancing the door.

' JAMES H. MoKEE. 

